The Diels-Alder reactivity of different bowl-shaped polycyclic aromatic hydrocarbons (namely, corannulene, cyclopentacorannulene, diindenochrysene, hemifullerene, and circumtrindene) has been explored computationally within the DFT framework. To this end, both the increase in reactivity with the size of the buckybowl and complete [6,6]-regioselectivity in the process have been analyzed in detail by using the activation strain model of reactivity in combination with the energy decomposition analysis method. These results have been compared with the parent C60 fullerene, which also produces the corresponding [6,6]-cycloadduct exclusively. The behavior of the buckybowls considered herein resembles, in general, that of C60. Whereas the interaction energy between the deformed reactants along the reaction coordinate mainly controls the regioselectivity of the process, it is the interplay between the activation strain energy and the transition-state interaction that governs the reactivity of the system. Bigger bowls, better reactivity: Starting from corannulene, there is a smooth convergence to the C60 energy barrier and reaction energy for the Diels-Alder reaction with cyclopentadiene when the size of the buckybowl is increased (see figure). Through density functional calculations, the origins of both this trend of reactivity and the observed exclusive [6,6]-regioselectivity are analyzed in detail

Abstract:

We are grateful for financial support from the Spanish MINECO-FEDER (grants CTQ2013-44303-P and CTQ2014-51912-REDC to I.F. and CTQ2014-54306-P to M.S.), Fundaciûn BBVA (Convocatoria 2015 de Ayudas Fundaciûn BBVA a Investigadores y Creadores Culturales), Catalan DIUE (projects 2014SGR931 and XRQTC to M.S.), the National Research School Combination—Catalysis (NRSC-C), and The Netherlands Organization for Scientific Research (NWO/ALW, NWO/CW, NWO/EW). Support for the research of M.S. was received through the ICREA Academia 2014 prize of the Catalan DIUE. The FEDER grant UNGI10-4E-801 (European Fund for Regional Development) also funded this research. Y.G.-R. acknowledges the MINECO for a FPI grant